package Test;

import java.util.Scanner;

public class test07 {
    public static void main(String[] args){
        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        int m = scan.nextInt();
        int x = scan.nextInt();
        int y = scan.nextInt();
        int[] dx = {0,0,1,-1};
        int[] dy = {1,-1,0,0};
        int[][] dp = new int[n+1][m+1];
        for(int i=0;i<n;i++) {
            if(check(i,0,x,y)) break;
            else dp[i][0] = 1;
        }
        for(int j=0;j<m;j++){
            if(check(0,j,x,y)) break;
            else dp[0][j] = 1;
        }
        for(int i=1;i<n;i++){
            for(int j=1;j<m;j++){
                if(check(i,j,x,y)){
                    dp[i][j] = 0;
                }else{
                    dp[i][j] = dp[i-1][j] + dp[i][j-1];
                }
            }
        }
        System.out.println(dp[n-1][m-1]);
    }
    public static boolean check(int i,int j,int x,int y){
        if(i!=x && j!=y && Math.abs(x-i)+ Math.abs(y-j)==3 || x==i && y==j)
            return true;
        return false;
    }
}
